VIII. MEASUREMENT. 329 



1412. Insulating Stand, with Air Chamber, artificially 

 dried by sulphuric acid, used in connexion with first portable 

 atmospheric electrometer. Sir William Thomson. 



This stand was ordinarily attached to the top of the electrometer, as figured 

 in NichoPs Cyclopaedia, Art. Electricity (atmospheric), and in Thomson's Ke- 

 print of Papers on Electrostatics and Magnetism, XVI., 263. Sometimes as 

 in observations to determine in absolute measure the electric force in the 

 atmosphere, on the sea beach, and in boats in Brodick Bay, Isle of Arran (re- 

 print XVI., 281), and, with the assistance of Dr. Joule, on the Links of 

 Aberdeen (British Association meeting, 1851) the stand was detached from 

 the electrometer and laid on the ground at a distance from it with connexion 

 by fine wire to the insulated part of the electrometer, which also was placed 

 on the ground, and was read by observer lying as close to the ground as 

 possible. 



1413. Atmospheric Portable Electrometer, No. 2, altered 

 for first trial of divided ring principle for a quadrant marine 

 electrometer, and used successfully on board the " Great Eastern/* 

 though not in connexion with the cable, in 1865. 



Sir William Thomson. 



This instrument has not been repeated, nor described in print, but it may 

 yet do good service at sea. Made by James White, Glasgow. 



1413a. Sir Wm. Thomson's Quadrant Electrometer, 



with most complete adjustments and of most perfect construction. 



James White. 



A descriptive pamphlet accompanies the instrument. 



1413b. Sir William Thomson's Portable Electro- 

 meter, with most complete adjustments, and of most perfect con- 

 struction. . James White. 



1413c. Electric Sensitizer. Sir William Thomson. 



This instrument is an induction electric machine, and is used with the port- 

 able electrometer or other electrometer for testing the potential of a conductor 

 without removing any part of its charge. 



1414. Atmospheric Portable Electrometer, No. 4, altered 

 to a plan for marine electrometer, which was discarded soon after 

 trial. Sir William Thomson. 



1415. Atmospheric Portable Electrometer, No. 5. Per- 

 fected portable electrometer, on same general plan as No. 1, 

 described fully in Friday Evening Lecture to the Royal Institu- 

 tion, May 18th, 1860 (Thomson's Reprint of Papers on Electro- 

 statics and Magnetism, XVI., 277). Made by James White, 

 Glasgow. Sir William Thomson. 



1416. Atmospheric Portable Electrometer, No. 10. 



First of new plan described in report on electrometers and electri- 

 cal measurements (British Association Report for 1867, Committee 



